I use that commands in Ubuntu 15.04:
sudo add-apt-repository ppa:tualatrix/ppa
sudo apt-get update
sudo apt-get install ubuntu-tweak
When I run sudo apt-get update
I get this error message:
W: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/vivid/main/source/Sources 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/vivid/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/vivid/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
Because of this error I can't install Ubuntu Tweak...
How can I solve this?